1 Features
1• Input Voltage Range: up to 20 V
• Voltage Options for Charging 1, 2, 3, or 4 Cells
• Output Current up to 15 mA
• Precision (0.5%) End-of-Charge Control
– LM3420 ±1%
– LM3420A ±0.5%
• Drive Capability for External Power Stage
• Temperature Drift Curvature Correction for
Voltage Stability
• Low Quiescent Current, 85 μA (Typ.)
• Tiny SOT-23-5 package

2 Applications
• Lithium-Ion Battery Charging
• Suitable for Linear and Switching Regulator
Charger Designs

3 Description
The LM3420 series of controllers are monolithic
integrated circuits designed for charging and end-of- charge control for lithium-ion rechargeable batteries.
The LM3420 is available in an 8.4-V version for one
through four cell charger applications.
Included in a very small package is an (internally
compensated) op amp, a bandgap reference, an NPN
output transistor, and voltage setting resistors. The amplifier's inverting input is externally accessible for
loop frequency compensation. The output is an open-
emitter NPN transistor capable of driving up to 15 mA
of output current into external circuitry.
A trimmed precision bandgap reference utilizes
temperature drift curvature correction for excellent
voltage stability over the operating temperature
range. The LM3420 series allows for precision end- of-charge voltage threshold for lithium-ion
rechargeable batteries. The premium grade LM3420A
is available with an initial voltage threshold tolerance
of ±0.5%, while the standard grade LM3420 has an
initial voltage threshold tolerance of ±1%.
The LM3420 is available in a sub-miniature 5-lead
surface mount package thus allowing very compact
designs.